Electronic device manufacture

ABSTRACT

Methods for depositing uniform, pinhole-defect free organic polysilica coatings are provided. These methods allow for the use of these materials as spin-on cap layers in the manufacture of integrated circuits.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of manufacture ofelectronic devices. In particular, this invention relates to themanufacture of integrated circuit devices containing low dielectricconstant material.

As electronic devices become smaller, there is a continuing desire inthe electronics industry to increase the circuit density in electroniccomponents, e.g., integrated circuits, circuit boards, multichipmodules, chip test devices, and the like without degrading electricalperformance, e.g., crosstalk or capacitive coupling, and also toincrease the speed of signal propagation in these components. One methodof accomplishing these goals is to reduce the dielectric constant of theinterlayer, or intermetal, insulating material used in the components.

A variety of organic and inorganic porous dielectric materials are knownin the art in the manufacture of electronic devices, particularlyintegrated circuits. Suitable inorganic dielectric materials includesilicon dioxide and organic polysilicas. Suitable organic dielectricmaterials include thermosets such as polyimides, polyarylene ethers,polyarylenes, polycyanurates, polybenzazoles, benzocyclobutenes,fluorinated materials such as poly(fluoroalkanes), and the like. Of theorganic polysilica dielectrics, the alkyl silsesquioxanes such as methylsilsesquioxane are of increasing importance because of their lowdielectric constant.

A method for reducing the dielectric constant of interlayer, orintermetal, insulating material is to incorporate within the insulatingfilm very small, uniformly dispersed pores or voids. In general, suchporous dielectric materials are prepared by first incorporating aremovable porogen into a B-staged dielectric material, disposing theB-staged dielectric material containing the removable porogen onto asubstrate, curing the B-staged dielectric material and then removing theporogen to form a porous dielectric material. For example, U.S. Pat. No.5,895,263 (Carter et al.) and U.S. Pat. No. 6,271,273 (You et al.)disclose processes for forming integrated circuits containing porousorganic polysilica dielectric material. In conventional processes, thedielectric material is typically cured under a non-oxidizing atmosphere,such as nitrogen, and optionally in the presence of an amine in thevapor phase to catalyze the curing process.

After the porous dielectric material is formed, it is subjected toconventional processing conditions of patterning, etching apertures,optionally applying a barrier layer and/or seed layer, metallizing orfilling the apertures, planarizing the metallized layer, and thenapplying a cap layer or etch stop. These process steps may then berepeated to form another layer of the device.

A disadvantage of certain dielectric materials, including organicpolysilica dielectric materials, is that they may not provide sufficientresistance to planarization techniques, such as chemical mechanicalplanarization (“CMP”) used in subsequent manufacturing steps orsufficient resistance to etching, such as oxygen plasma, duringphotoresist removal from such dielectric materials. One solution to thisis to use a layer of a different material atop the dielectric material(i.e. a cap layer) to provide the desired characteristics. Cap layersare useful in both single and dual damascene processes, particularlywhen porous dielectric materials are used. These layers planarize thesurface of the dielectric by filling any surface defects, provide adenser matrix than that of the dielectric so as to seal any porosityhaving connectivity to the surface of the dielectric film (preventsintrusion of any residues from subsequent processing into the porousdielectric), improve the adhesion with subsequently applied layers ofmaterial and provide a hardmask having sufficient resistance tosubsequent processing steps and etch differential between it and theunderlying porous dielectric layer to allow sequential selective patterntransfers between successive layers of photoimaged pattern, cap layerand dielectric. Suitable cap layer compositions must be able to providegood coating uniformity in the required thickness range (e.g., 100 to600 Å) and have a low dielectric constant (k≦3.5).

Although certain organic cap layers have recently been recommended, suchas poly(arylene ethers), typical cap layers are based on silicondioxide, silicon carbide, silicon nitride, silicon oxynitride and thelike. For example, a conventional poly(arylene ether) dielectricmaterial may have a non-porous methyl silsesquioxane capping layer, oralternatively, a conventional methyl silsesquioxane dielectric layer mayhave a non-porous poly(arylene ether) capping layer. U.S. PatentApplication No. 2001/0051447 A1 (Usami) discloses a methylsilsesquioxane dielectric layer having a silicon oxide capping layer toimprove the etch resistance.

Chemical vapor deposition (“CVD”) methods are conventionally used todeposit cap layers on the underlying dielectric material. The carriergas used in the CVD methods can generate amines, which in turn can leadto a poisoning of an overlaid photoresist layer, necessitating the useof either an N₂O ashing step of the application of a barrier materialbetween the cap layer and the photoresist. This problem can beeliminated by a spin-on process for the cap layer material. Spin-onmethods for depositing cap layers are not without drawbacks. The majorproblem is assuring a uniform, defect-free coating of the cap layermaterial, particularly when an inorganic or organic-inorganic materialis used as the cap layer. Organic polysilica materials, such as methylsilsesquioxane, often suffer from poor coating uniformity, pinholedefects, and crack formation during curing.

Thus, there is a need for methods for depositing cap layers,particularly organic polysilica cap layers, on a dielectric materialthat overcome the above problems.

SUMMARY OF THE INVENTION

It has been surprisingly found that cap layers containing organicpolysilica material, such as alkyl and/or aryl silsesquioxane, can beprepared easily deposited on a dielectric material by spin-coating.Uniform and pinhole defect-free coatings of such cap layers have beenachieved according to the present invention.

The present invention provides a method for depositing an organicpolysilica cap layer on a dielectric material including the steps of: a)disposing a cap layer composition on a dielectric material, the caplayer composition including one or more B-staged organic polysilicaresins and one or more coating enhancers; and b) at least partiallycuring the one or more B-staged organic polysilica resins to form a caplayer; wherein the one or more coating enhancers are present in anamount sufficient to provide a pinhole-free cap layer. The coatingenhancers may then be removed prior to or during the step of completelycuring the organic polysilica cap layer resin.

In another aspect, the present invention provides a method formanufacturing a device including the steps of: a) providing a dielectricmaterial; b) disposing a cap layer composition on a dielectric material,the cap layer composition including one or more B-staged organicpolysilica resins and one or more coating enhancers; and b) at leastpartially curing the one or more B-staged organic polysilica resins toform a cap layer; wherein the one or more coating enhancers are presentin an amount sufficient to provide a pinhole-free cap layer.

In a further aspect, the present invention provides a method formanufacturing a device including the steps of: a) providing a dielectricmaterial; b) disposing a cap layer composition on a dielectric material,the cap layer composition including one or more B-staged organicpolysilica resins and removable porogen; and b) at least partiallycuring the one or more B-staged organic polysilica resin to form a caplayer; wherein the removable porogen is present in an amount sufficientto provide a pinhole-free cap layer.

In yet another aspect, the present invention provides a structureincluding a first layer of an organic polysilica dielectric material anda second layer disposed on the first layer, wherein the second layer isa composition including one or more B-staged organic polysilica resinsand removable porogen, wherein the porogen is present in an amountsufficient to provide a pinhole-free second layer. Also included arestructures wherein the second layer is at least partially cured.

Also provided by this invention is a structure including a porous firstlayer of an organic polysilica dielectric material and a porous caplayer disposed on the dielectric material. Preferably, the cap layerincludes an organic polysilica material.

Further, this invention provides a structure including a layer of adielectric material and porous cap layer disposed on the dielectricmaterial.

Structures including a porous first layer of an organic polysilicadielectric material having a first etch selectivity and a porous caplayer disposed on the dielectric material having a second etchselectivity, wherein the difference in etch selectivities is 10% orgreater are also provided.

In a still further aspect, this invention provides a structure includinga dielectric layer having a dielectric constant of <3 and an organicpolysilica cap layer disposed on the dielectric layer, wherein theorganic polysilica cap layer has a dielectric constant of ≦2.9.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a scanning electron micrograph (“SEM”) of a spin-coatedorganic polysilica cap layer having pinhole defects.

FIG. 2 is a SEM of a spin-coated organic polysilica cap layer preparedfrom a B-staged organic polysilica resin containing 3% by weightcompatibilized porogen and having pinhole defects.

FIG. 3 is a SEM of a spin-coated organic polysilica cap layer preparedfrom a B-staged organic polysilica resin containing 10% by weightcompatibilized porogen and having no pinhole defects.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification, the following abbreviations shallhave the following meanings, unless the context clearly indicatesotherwise: ° C.=degrees centigrade; UV=ultraviolet; nm=nanometer;g=gram; wt %=weight percent; L=liter; μm=micron=micrometer;rpm=revolutions per minute; N=normal; ca.=approximately; DI=deionized;and ppm=parts per million.

The term “alkyl” includes straight chain, branched and cyclic alkylgroups. The term “porogen” refers to a pore forming material, e.g. apolymeric material or particle dispersed in a material that issubsequently removed to yield pores in the material. Thus, the terms“removable porogen,” “removable polymer” and “removable particle” areused interchangeably throughout this specification. “Porous” refers to amaterial that has been intentionally made porous, such as by the use ofa porogen. As used herein, “dense” refers to material that has not beenintentionally made porous. “Cross-linker” and “crosslinking agent” areused interchangeably throughout this specification. “Polymer” refers topolymers and oligomers, and also includes homopolymers and copolymers.The terms “oligomer” and “oligomeric” refer to dimers, trimers,tetramers and the like. “Monomer” refers to any ethylenically oracetylenically unsaturated compound capable of being polymerized orother compound capable of being polymerized by condensation. Suchmonomers may contain one or more double or triple bonds or groupscapable of being polymerized by condensation.

The term “B-staged” refers to uncured organic polysilica materials. By“uncured” is meant any material that can be polymerized or cured to formhigher molecular weight materials, such as coatings or films. As usedherein, “partially cured” refers to a film or coating of organicpolysilica resin or material that has been sufficiently cured so thatonly 1% or less of the thickness of the film is lost upon contact with asolvent suitable for dissolving the B-staged organic polysilica resin.Such partially cured films or coatings may undergo further curing duringsubsequent processing steps. “Films” and “Layers” are usedinterchangeably throughout this Specification. B-staged materials may bemonomeric, oligomeric or mixtures thereof. B-staged material is furtherintended to include mixtures of polymeric material with monomers,oligomers or a mixture of monomers and oligomers.

Unless otherwise noted, all amounts are percent by weight and all ratiosare by weight. All numerical ranges are inclusive and combinable in anyorder, except where it is clear that such numerical ranges areconstrained to add up to 100%.

Organic polysilica cap layers can be deposited on a dielectric materialincluding the steps of: a) disposing a cap layer composition on adielectric material, the cap layer composition including one or moreB-staged organic polysilica resins and one or more coating enhancers;and b) at least partially curing the one or more B-staged organicpolysilica resins to form a cap layer; wherein the one or more coatingenhancers are present in an amount sufficient to provide a pinhole-freecap layer. The term “cap layer” refers to any layer added to the top ofa dielectric material and which performs one or more of the followingfunctions: 1) fills any surface defects of the dielectric material; 2)provides a denser matrix than that of the dielectric so as to seal anyporosity having connectivity to the surface of the dielectric film,which prevents intrusion of any residues from subsequent processing intothe porous dielectric; 3) improves the adhesion of the dielectric layerwith subsequently applied layers of material; and 4) provides a hardmaskhaving sufficient resistance to subsequent processing steps and etchdifferential between it and the underlying porous dielectric layer toallow sequential selective pattern transfers between successive layersof photoimaged pattern, cap layer and dielectric. “Cap layers”, as theterm is generally used herein, include those layers functioning as etchstops, CMP stops, hardmasks and the like and are typically applied to adielectric or insulating layer.

The present cap layer compositions include one or more B-staged organicpolysilica resins and one or more coating enhancers. By “organicpolysilica resin” (or organo siloxane) is meant a compound includingsilicon, carbon, oxygen and hydrogen atoms. Exemplary organic polysilicaresins are hydrolyzates and partial condensates of one or more silanesof formulae (I) or (II):R_(a)SiY_(4-a)   (I)R¹ _(b)(R²O)_(3-b)Si(R³)_(c)Si(OR⁴)₃₋₄R⁵ _(d)   (II)wherein R is hydrogen, (C₁-C₈)alkyl, (C₇-C₁₂)arylalkyl, substituted(C₇-C₁₂)arylalkyl, aryl, and substituted aryl; Y is any hydrolyzablegroup; a is an integer of 0 to 2; R¹, R², R⁴ and R⁵ are independentlyselected from hydrogen, (C₁-C₆)alkyl, (C₇-C₁₂)arylalkyl, substituted(C₇-C₁₂)arylalkyl, aryl, and substituted aryl; R³ is selected from(C₁-C₁₀)alkyl, —(CH₂)_(h)—, —(CH₂)_(h1)-E_(k)-(CH₂)_(h2)—, —(CH₂)_(h)-Z,arylene, substituted arylene, and arylene ether; E is selected fromoxygen, NR⁶ and Z; Z is selected from aryl and substituted aryl; R⁶ isselected from hydrogen, (C₁-C₆)alkyl, aryl and substituted aryl; b and dare each an integer of 0 to 2; c is an integer of 0 to 6; and h, h1, h2and k are independently an integer from 1 to 6; provided that at leastone of R, R¹, R³ and R⁵ is not hydrogen. “Substituted arylalkyl”,“substituted aryl” and “substituted arylene” refer to an arylalkyl, arylor arylene group having one or more of its hydrogens replaced by anothersubstituent group, such as cyano, hydroxy, mercapto, halo, (C₁-C₆)alkyl,(C₁-C₆)alkoxy, and the like.

It is preferred that R is (C₁-C₄)alkyl, benzyl, hydroxybenzyl, phenethylor phenyl, and more preferably methyl, ethyl, iso-butyl, tert-butyl orphenyl. Preferably, a is 1. Suitable hydrolyzable groups for Y include,but are not limited to, halo, (C₁-C₆)alkoxy, acyloxy and the like.Preferred hydrolyzable groups are chloro and (C₁-C₂)alkoxy. Suitableorganosilanes of formula (I) include, but are not limited to, methyltrimethoxysilane, methyl triethoxysilane, phenyl trimethoxysilane,phenyl triethoxysilane, tolyl trimethoxysilane, tolyl triethoxysilane,propyl tripropoxysilane, iso-propyl triethoxysilane, iso-propyltripropoxysilane, ethyl trimethoxysilane, ethyl triethoxysilane,iso-butyl triethoxysilane, iso-butyl trimethoxysilane, tert-butyltriethoxysilane, tert-butyl trimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyl triethoxysilane, benzyl trimethoxysilane,benzyl triethoxysilane, phenethyl trimethoxysilane, hydroxybenzyltrimethoxysilane, hydroxyphenylethyl trimethoxysilane andhydroxyphenylethyl triethoxysilane.

Organosilanes of formula (II) preferably include those wherein R¹ and R⁵are independently (C₁-C₄)alkyl, benzyl, hydroxybenzyl, phenethyl orphenyl. Preferably R¹ and R⁵ are methyl, ethyl, tert-butyl, iso-butyland phenyl. It is also preferred that b and d are independently 1 or 2.Preferably R³ is (C₁-C₁₀)alkyl, —(CH₂)_(h)—, arylene, arylene ether and—(CH₂)_(h1)-E-(CH₂)_(h2). Suitable compounds of formula (II) include,but are not limited to, those wherein R³ is methylene, ethylene,propylene, butylene, hexylene, norbornylene, cycloheylene, phenylene,phenylene ether, naphthylene and —CH₂—C₆H₄—CH₂—. It is further preferredthat c is 1 to 4.

Suitable organosilanes of formula (II) include, but are not limited to,bis(hexamethoxysilyl)methane, bis(hexaethoxysilyl)methane,bis(hexaphenoxysilyl)methane, bis(dimethoxymethylsilyl)methane,bis(diethoxymethyl-silyl)methane, bis(dimethoxyphenylsilyl)methane,bis(diethoxyphenylsilyl)methane, bis(methoxydimethylsilyl)methane,bis(ethoxydimethylsilyl)methane, bis(methoxy-diphenylsilyl)methane,bis(ethoxydiphenylsilyl)methane, bis(hexamethoxysilyl)ethane,bis(hexaethoxysilyl)ethane, bis(hexaphenoxysilyl)ethane,bis(dimethoxymethylsilyl) ethane, bis(diethoxymethylsilyl)ethane,bis(dimethoxyphenylsilyl)ethane, bis(diethoxyphenyl-silyl)ethane,bis(methoxydimethylsilyl)ethane, bis(ethoxydimethylsilyl)ethane,bis(methoxy-diphenylsilyl)ethane, bis(ethoxydiphenylsilyl)ethane,1,3-bis(hexamethoxysilyl))propane, 1,3-bis(hexaethoxysilyl)propane,1,3-bis(hexaphenoxysilyl)propane, 1,3-bis(dimethoxy-methylsilyl)propane,1,3-bis(diethoxymethylsilyl)propane,1,3-bis(dimethoxyphenyl-silyl)propane,1,3-bis(diethoxyphenylsilyl)propane,1,3-bis(methoxydimehylsilyl)propane,1,3-bis(ethoxydimethylsilyl)propane,1,3-bis(methoxydiphenylsilyl)propane, and1,3-bis(ethoxydiphenylsilyl)propane. Preferred of these arehexamethoxydisilane, hexaethoxydisilane, hexaphenoxydisilane,1,1,2,2-tetramethoxy-1,2-dimethyldisilane,1,1,2,2-tetraethoxy-1,2-dimethyldisilane,1,1,2,2-tetramethoxy-1,2-diphenyldisilane,1,1,2,2-tetraethoxy-1,2-diphenyldisilane,1,2-dimethoxy-1,1,2,2-tetramethyldisilane,1,2-diethoxy-1,1,2,2-tetramethyldisilane,1,2-dimethoxy-1,1,2,2-tetraphenyldisilane,1,2-diethoxy-1,1,2,2-tetraphenyl-disilane, bis(hexamethoxysilyl)methane,bis(hexaethoxysilyl)methane, bis(dimethoxymethyl-silyl)methane,bis(diethoxymethylsilyl)methane, bis(dimethoxyphenylsilyl)methane,bis(diethoxyphenylsilyl)methane, bis(methoxydimethylsilyl)methane,bis(ethoxydimethyl-silyl)methane, bis(methoxydiphenylsilyl)methane, andbis(ethoxydiphenylsilyl)methane.

When the B-staged organic polysilica resins include one or more of ahydrolyzate and partial condensate of organosilanes of formula (II), cmay be 0, provided that at least one of R¹ and R are not hydrogen. In analternate embodiment, the B-staged organic polysilica resins may includeone or more of a cohydrolyzate and partial cocondensate of organosilanesof both formulae (I) and (II). In such cohydrolyzates and partialcocondensates, c in formula (II) can be 0, provided that at least one ofR, R¹ and R⁵ is not hydrogen. Suitable silanes of formula (II) where cis 0 include, but are not limited to, hexamethoxydisilane,hexaethoxydisilane, hexaphenoxydisilane,1,1,1,2,2-pentamethoxy-2-methyldisilane,1,1,1,2,2-pentaethoxy-2-methyldisilane,1,1,1,2,2-pentamethoxy-2-phenyldisilane,1,1,1,2,2-pentaethoxy-2-phenyldisilane,1,1,2,2-tetramethoxy-1,2-dimethyldisilane,1,1,2,2-tetraethoxy-1,2-dimethyldisilane,1,1,2,2-tetramethoxy-1,2-diphenyldisilane,1,1,2,2-tetraethoxy-1,2-diphenyldisilane,1,1,2-trimethoxy-1,2,2-trimethyldisilane,1,1,2-triethoxy-1,2,2-trimethyldisilane,1,1,2-trimethoxy-1,2,2-triphenyldisilane,1,1,2-triethoxy-1,2,2-triphenyldisilane,1,2-dimethoxy-1,1,2,2-tetramethyldisilane,1,2-diethoxy-1,1,2,2-tetramethyldisilane,1,2-dimethoxy-1,1,2,2-tetraphenyldisilane, and1,2-diethoxy-1,1,2,2-tetra-phenyldisilane.

In one embodiment, particularly suitable B-staged organic polysilicaresins are chosen from one or more of hydrolyzates and partialcondensates of compounds of formula (I). Such B-staged organicpolysilica resins have the formula (III):((R⁷R⁸SiO)_(c)(R⁹SiO_(1.5))_(f)(R¹⁰SiO_(1.5))_(g)(SiO₂)_(r))_(n)   (III)wherein R⁷, R⁸, R⁹ and R¹⁰ are independently selected from hydrogen,(C₁-C₆)alkyl, (C₇-C₁₂)arylalkyl, substituted (C₇-C₁₂)arylalkyl, aryl,and substituted aryl; e, g and r are independently a number from 0 to 1;f is a number from 0.2 to 1; n is integer from 3 to 10,000; providedthat e+f+g+r=1; and provided that at least one of R⁷, R⁸ and R⁹ is nothydrogen. In the above formula (III), e, f, g and r represent the moleratios of each component. Such mole ratios can be varied between 0and 1. It is preferred that e is from 0 to 0.8. It is also preferredthat g is from 0 to 0.8. It is further preferred that r is from 0 to0.8. In the above formula, n refers to the number of repeat units in theB-staged material. Preferably, n is an integer from 3 to 1000.

Suitable organic polysilica resins include, but are not limited to,silsesquioxanes, partially condensed halosilanes or alkoxysilanes suchas partially condensed by controlled hydrolysis tetraetboxysilane havingnumber average molecular weight of 500 to 20,000, organically modifiedsilicates having the composition RSiO₃, O₃SiRSiO₃, R₂SiO₂ and O₂SiR₃SiO₂wherein R is an organic substituent, and partially condensedorthosilicates having Si(OR)₄ as the monomer unit. Silsesquioxanes arepolymeric silicate materials of the type RSiO_(1.5) where R is anorganic substituent. Suitable silsesquioxanes are alkyl silsesquioxanessuch as methyl silsesquioxane, ethyl silsesquioxane, propylsilsesquioxane, butyl silsesquioxane and the like; aryl silsesquioxanessuch as phenyl silsesquioxane and tolyl silsesquioxane; alkyl/arylsilsesquioxane mixtures such as a mixture of methyl silsesquioxane andphenyl silsesquioxane; and mixtures of alkyl silsesquioxanes such asmethyl silsesquioxane and ethyl silsesquioxane. B-staged silsesquioxanematerials include homopolymers of silsesquioxanes, copolymers ofsilsesquioxanes or mixtures thereof. Such materials are generallycommercially available or may be prepared by known methods.

In an alternate embodiment, the organic polysilica resins may contain awide variety of other monomers in addition to the silicon-containingmonomers described above. For example, the organic polysilica resins mayfurther comprise cross-linking agents, and carbosilane moieties. Suchcross-linking agents may be any of the cross-linking agents describedelsewhere in this specification, or any other known cross-linkers forsilicon-containing materials. It will be appreciated by those skilled inthe art that a combination of cross-linkers may be used. Carbosilanemoieties refer to moieties having a (Si—C), structure, such as(Si-A)_(x) structures wherein A is a substituted or unsubstitutedalkylene or arylene, such as SiR₃CH₂—, —SiR₂CH₂—, ═SiRCH₂—, and ≡SiCH₂—,where R is usually hydrogen but may be any organic or inorganic radical.Suitable inorganic radicals include organosilicon, siloxyl, or silanylmoieties. These carbosilane moieties are typically connected“head-to-tail”, i.e. having Si—C—Si bonds, in such a manner that acomplex, branched structure results. Particularly useful carbosilanemoieties are those having the repeat units (SiH_(x)CH₂) and(SiH_(y-1)(CH═CH₂)CH₂), where x=0 to 3 and y=1 to 3. These repeat unitsmay be present in the organic polysilica resins in any number from 1 to100,000, and preferably from 1 to 10,000. Suitable carbosilaneprecursors are those disclosed in U.S. Pat. No. 5,153,295 (Whitmarsh etal.) and U.S. Pat. No. 6,395,649 (Wu).

It is preferred that the B-staged organic polysilica resin includes asilsesquioxane, and more preferably methyl silsesquioxane, ethylsilsesquioxane, propyl silsesquioxane, iso-butyl silsesquioxane,tert-butyl silsesquioxane, phenyl silsesquioxane, tolyl silsesquioxane,benzyl silsesquioxane or mixtures thereof. Methyl silsesquioxane, phenylsilsesquioxane and mixtures thereof are particularly suitable. Otheruseful silsesquioxane mixtures include mixtures of hydridosilsesquioxanes with alkyl, aryl or alkyl/aryl silsesquioxanes.Typically, the silsesquioxanes useful in the present invention are usedas oligomeric materials, generally having from 3 to 10,000 repeatingunits.

Particularly suitable organic polysilica B-staged resins areco-hydrolyzates and partial condensates of one or more organosilanes offormulae (I) and/or (II) and one or more tetrafunctional silanes havingthe formula SiY₄, where Y is any hydrolyzable group as defined above.Suitable hydrolyzable groups include, but are not limited to, halo,(C₁-C₆)alkoxy, acyloxy and the like. Preferred hydrolyzable groups arechloro and (C₁-C₂)alkoxy. Suitable tetrafunctional silanes of theformula SiY₄ include, but are not limited to, tetramethoxysilane,tetraethoxysilane, tetrachlorosilane, and the like. Particularlysuitable silane mixtures for preparing the cohydrolyzates and partialcocondensates include: methyl triethoxysilane and tetraethoxysilane;methyl trimethoxysilane and tetramethoxysilane; phenyl triethoxysilaneand tetraethoxysilane; methyl triethoxysilane and phenyl triethoxysilaneand tetraethoxysilane; ethyl triethoxysilane and tetramethoxysilane; andethyl triethoxysilane and tetraethoxysilane. The ratio of suchorganosilanes to tetrafunctional silanes is typically from 99:1 to 1:99,preferably from 95:5 to 5:95, more preferably from 90:10 to 10:90, andstill more preferably from 80:20 to 20:80.

In a particular embodiment, the B-staged organic polysilica resin ischosen from one or more of a co-hydrolyzate and partial co-condensate ofone or more organosilanes of formula (I) and a tetrafunctional silane offormula SiY₄. In another embodiment, the B-staged organic polysilicaresin is chosen from one or more of a co-hydrolyzate and partialco-condensate of one or more organosilanes of formula (II) and atetrafunctional silane of formula SiY₄. In still another embodiment, theB-staged organic polysilica resin is chosen from one or more of aco-hydrolyzate and partial co-condensate of one or more organosilanes offormula (I), one or more silanes of formula (II) and a tetrafunctionalsilane of formula SiY₄. The B-staged organic polysilica resins includeone or more of a non-hydrolyzed and non-condensed silane of one or moresilanes of formulae (I) or (II) with one or more of the hydrolyzate andpartial condensate of one or more silanes of formulae (I) or (II). In afurther embodiment, the B-staged organic polysilica resin includes asilane of formula (II) and one or more of a hydrolyzate and partialcondensate of one or more organosilanes of formula (I), and preferablyone or more of a co-hydrolyzate and partial co-condensate of one or moreorganosilanes of formula (I) with a tetrafunctional silane of theformula SiY₄ where Y is as defined above. Perferably, such B-stagedorganic polysilica resin includes a mixture of one or more silanes offormula (II) and one or more of a co-hydrolyzate and partialco-condensate having the formula (RSiO_(1.5)) (SiO₂) where R is asdefined above.

When organosilanes of formula (I) are co-hydrolyzed or co-condensed witha tetrafunctional silane, it is preferred that the organosilane offormula (I) has the formula RSiY₃, and preferably is selected frommethyl trimethoxysilane, methyl triethoxysilane, ethyl trimethoxysilane,ethyl triethoxysilane, phenyl trimethoxysilane, phenyl triethoxysilaneand mixtures thereof. It is also preferred that the tetrafunctionalsilane is selected from tetramethoxysilane and tetraethoxysilane.

In another embodiment, particularly useful cap layer compositionsinclude one or more B-staged organic polysilica resins having theformula

wherein each R¹ and R² are independently selected from hydroxyl,hydrogen, (C₁-C₆)alkyl, (C₂-C₆)alkenyl, and (C₁-C₆)alkylidine; x=0.3 to0.7; and y+z=0.3 to 0.7; wherein x and y+z=the mole fraction of thecomponents. When x+y+z does not equal 1, then it is understood that oneor more other monomer units are included in the resin. Such othermonomer units may be any which can co-condense with the monomer units ofthe above formula, and preferably are one or more of the above describedsilanes. In one embodiment, x+y+z=1. In another embodiment, R¹ and R²are independently selected from hydroxyl, hydrogen methyl, ethyl, vinyl,methylidine (—CH₂—) and ethylidine (—CH₂CH₂—). A particularly usefulcomposition of this formula is where R¹ is methyl; R² is hydroxyl; x=0.5 to 0.6; and y+z=0.5 to 0.4. Such composition is prepared by theco-hydrolysis or co-condensation of methyl triethoxysilane andtetraethoxysilane. In general, resins having the above formula have amolecular weight of from 4000 to 100,000.

Any compound that provides an organic polysilica cap layer on adielectric material wherein the cap layer is uniform and pinholedefect-free may be used as the present coating enhancers. As usedherein, “pinhole” refers to a hole, such as from a few angstroms to 10nm in diameter, that communicates through the cap layer from a topsurface to a bottom surface and results from the deposition of the caplayer. Such pinholes are typically channels that are substantiallycircular in cross-section. The term “pinhole” does not include rips,tears or other mechanical defects and does not include intentionallyformed pores such as by the use of a porogen.

In general, the coating enhancers are substantially non-aggregated ornon-agglomerated in the B-staged material. Such non-aggregation ornon-agglomeration reduces or avoids the problem of killer (very large)pore or channel formation in the cured or partially cured resinmaterial, and is achieved by making the coating enhancer substantiallycompatible with the B-staged organic polysilica resin. By “substantiallycompatible” is meant that a composition of B-staged organic polysilicaresin and coating enhancer is slightly cloudy or slightly opaque.Preferably, “substantially compatible” means at least one of a solutionof the B-staged resin and coating enhancer, and a film or layerincluding a composition of B-staged resin and coating enhancer isslightly cloudy or slightly opaque. To be compatible, the coatingenhancer must be soluble in or miscible in the B-staged resin, in thesolvent used to dissolve the B-staged resin or both. Preferably, thecoating enhancer must be soluble in or miscible in the B-staged organicpolysilica resin.

The coating enhancers are preferably removable, meaning that they aresufficiently labile under certain conditions to be removed from theresulting cap layer. In one embodiment, the coating enhancers areremoved and no pores are formed. In an alternate embodiment, the coatingenhancers are removed to provide pores in the cap layer. As the purposeof a cap layer, inter alia, is to provide a sealing layer over a porousdielectric layer, and to act as a stop layer for certain processes suchas CMP, the cap layer typically needs to be dense only until the purposeof the cap layer has been fulfilled. For example, when the cap layer isa CMP stop, it needs to remain dense until the surface of the device hasbeen planarized. After such planarization, the cap layer may be madeporous.

Exemplary coating enhancers include, without limitation, high boilingsolvents, surfactants and removable polymers (porogens). “High boilingsolvents” refers to solvents having a boiling point of ≧200° C. atatmospheric pressure, and preferably ≧250° C. Useful surfactants are anythat contain poly(alkylene oxide) moieties or silicon-containingmoieties. Preferred poly(alkylene oxide)-containing surfactants areethylene oxide (“EO”) or propylene oxide (“PO”) polymers or copolymersof EO/PO. Exemplary poly(alkylene oxide) surfactants are polyethyleneglycol and polypropylene glycol. Useful molecular weight ranges for thepoly(alkylene oxide) surfactants are 100 to 50,000, preferably 200 to20,000 and more preferably 250 to 5000. Particularly usefulpoly(alkylene oxide) surfactants are those sold under the PLURONIC andTETRONIC brands by BASF, Ludwigshafen, Germany. A wide variety ofsilicon-containing surfactants may be used, such as those sold under theSILWET brand.

A wide variety of removable polymers (porogens) may be used as thecoating enhancers. The removable porogens may be polymers (linear,branched or particles) or may be co-polymerized with an organicpolysilica dielectric monomer to form a block copolymer having a labile(removable) component. Such polymers are preferably compatible asdescribed above. Suitable compatibilized porogens are those disclosed inU.S. Pat. No. 6,271,273 (You et al.) and European Patent Application EPApplication No. 1 088 848 (Allen et al.). In one embodiment, thecompatibilized porogen is a polymer that includes as polymerized unitsat least one compound selected from silyl-containing monomers andpoly(alkylene oxide) monomers. The silyl containing monomers orpoly(alkylene oxide) monomers may be used to form the uncrosslinkedpolymer, used as the crosslinker, or both. Other suitable removableparticles are those disclosed in U.S. Pat. No. 5,700,844.

Any monomer containing silicon may be useful as the silyl-containingmonomers. The silicon moiety in such silyl containing monomers may bereactive or unreactive. Exemplary “reactive” silyl containing monomersinclude those containing one or more alkoxy or acetoxy groups, such as,but not limited to, trimethoxysilyl containing monomers, triethoxysilylcontaining monomers, methyl dimethoxysilyl containing monomers, and thelike. Exemplary “unreactive” silyl containing monomers include thosecontaining alkyl groups, aryl groups, alkenyl groups or mixturesthereof, such as but are not limited to, trimethylsilyl containingmonomers, triethylsilyl containing monomers, phenyldimethylsilylcontaining monomers, and the like. Polymeric porogens including silylcontaining monomers as polymerized units are intended to include suchporogens prepared by the polymerization of a monomer containing a silylmoiety. It is not intended to include a linear polymer that contains asilyl moiety only as end capping units.

Suitable silyl containing monomers include, but are not limited to,vinyltrimethylsilane, vinyltriethylsilane, vinyltrimethoxysilane,vinyltriethoxysilane, y-trimethoxysilylpropyl (meth)acrylate,divinylsilane, trivinylsilane, dimethyldivinylsilane,divinylmethylsilane, methyltrivinylsilane, diphenyldivinylsilane,divinylphenylsilane, trivinylphenylsilane, divinylmethylphenylsilane,tetravinylsilane, dimethylvinyldisiloxane, poly(methylvinylsiloxane),poly(vinylhydrosiloxane), poly(phenylvinylsiloxane),allyloxy-tert-butyldimethylsilane, allyloxytrimethylsilane,allyltriethoxysilane, allyltri-iso-propylsilane, allyltrimethoxysilane,allyltrimethylsilane, allyltriphenylsilane, diethoxy methylvinylsilane,diethyl methylvinylsilane, dimethyl ethoxyvinylsilane, dimethylphenylvinylsilane, ethoxy diphenylvinylsilane, methylbis(trimethylsilyloxy)vinylsilane, triacetoxyvinylsilane,triethoxyvinylsilane, triethylvinylsilane, triphenylvinylsilane,tris(trimethylsilyloxy)vinylsilane, vinyloxytrimethylsilane and mixturesthereof.

The amount of silyl containing monomer useful to form the porogens ofthe present invention is typically from 1 to 99 % wt, based on the totalweight of the monomers used. It is preferred that the silyl containingmonomers are present in an amount of from 1 to 80 % wt, and morepreferably from 5 to 75 % wt.

Suitable poly(alkylene oxide) monomers include, but are not limited to,poly(propylene oxide) monomers, poly(ethylene oxide) monomers,poly(ethylene oxide/propylene oxide) monomers, poly(propylene glycol)(meth)acrylates, poly(propylene glycol) alkyl ether (meth)acrylates,poly(propylene glycol) phenyl ether (meth)acrylates, poly(propyleneglycol) 4-nonylphenol ether (meth)acrylates, poly(ethylene glycol)(meth)acrylates, poly(ethylene glycol) alkyl ether (meth)acrylates,poly(ethylene glycol) phenyl ether (meth)acrylates,poly(propylene/ethylene glycol) alkyl ether (meth)acrylates and mixturesthereof. Preferred poly(alkylene oxide) monomers includetrimethoylolpropane ethoxylate tri(meth)acrylate, trimethoylolpropanepropoxylate tri(meth)acrylate, poly(propylene glycol) methyl etheracrylate, and the like. Particularly suitable poly(propylene glycol)methyl ether acrylate monomers are those having a molecular weight inthe range of from 200 to 2000. The poly(ethylene oxide/propylene oxide)monomers useful in the present invention may be linear, block or graftcopolymers. Such monomers typically have a degree of polymerization offrom 1 to 50, and preferably from 2 to 50.

Typically, the amount of poly(alkylene oxide) monomers useful in theporogens of the present invention is from I to 99 % wt, based on thetotal weight of the monomers used. The amount of poly(alkylene oxide)monomers is preferably from 2 to 90 % wt, and more preferably from 5 to80 % wt.

The silyl containing monomers and the poly(alkylene oxide) monomers maybe used either alone or in combination to form the porogens of thepresent invention. In general, the amount of the silyl containingmonomers or the poly(alkylene oxide) monomers needed to compatiblize theporogen with the dielectric matrix depends upon the level of porogenloading desired in the matrix, the particular composition of the organopolysilica dielectric matrix, and the composition of the porogenpolymer. When a combination of silyl containing monomers and thepoly(alkylene oxide) monomers is used, the amount of one monomer may bedecreased as the amount of the other monomer is increased. Thus, as theamount of the silyl containing monomer is increased in the combination,the amount of the poly(alkylene oxide) monomer in the combination may bedecreased.

The polymers suitable for use as porogens in the present invention arepreferentially derived from one or more ethylenically or acetylenicallyunsaturated monomers including as polymerized units one or morecompounds selected from silyl containing monomers and poly(alkyleneoxide) monomers and more preferable include one or more cross-linkingagents. Polymeric porogen particles contain one or more cross-linkingagents. Suitable monomers which may be copolymerized with the one ormore silyl containing monomers or one or more poly(alkylene oxide)monomers or mixtures thereof include, but are not limited to:(meth)acrylic acid, (meth)acrylamides, alkyl (meth)acrylates, alkenyl(meth)acrylates, aromatic (meth)acrylates, vinyl aromatic monomers,nitrogen-containing compounds and their thio-analogs, and substitutedethylene monomers.

Typically, the alkyl (meth)acrylates useful in the present invention are(C₁-C₂₄) alkyl (meth)acrylates. Suitable alkyl (meth)acrylates include,but are not limited to, “low cut” alkyl (meth)acrylates, “mid cut” alkyl(meth)acrylates and “high cut” alkyl (meth)acrylates.

“Low cut” alkyl (meth)acrylates are typically those where the alkylgroup contains from 1 to 6 carbon atoms. Suitable low cut alkyl(meth)acrylates include, but are not limited to: methyl methacrylate,methyl acrylate, ethyl acrylate, propyl methacrylate, butylmethacrylate, butyl acrylate, isobutyl methacrylate, hexyl methacrylate,cyclohexyl methacrylate, cyclohexyl acrylate and mixtures thereof.

“Mid cut” alkyl (meth)acrylates are typically those where the alkylgroup contains from 7 to 15 carbon atoms. Suitable mid cut alkyl(meth)acrylates include, but are not limited to: 2-ethylhexyl acrylate,2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate,isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate (alsoknown as lauryl methacrylate), tridecyl methacrylate, tetradecylmethacrylate (also known as myristyl methacrylate), pentadecylmethacrylate and mixtures thereof. Particularly useful mixtures includedodecyl-pentadecyl methacrylate, a mixture of linear and branchedisomers of dodecyl, tridecyl, tetradecyl and pentadecyl methacrylates;and lauryl-myristyl methacrylate.

“High cut” alkyl (meth)acrylates are typically those where the alkylgroup contains from 16 to 24 carbon atoms. Suitable high cut alkyl(meth)acrylates include, but are not limited to: hexadecyl methacrylate,heptadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate,cosyl methacrylate, eicosyl methacrylate and mixtures thereof.Particularly useful mixtures of high cut alkyl (meth)acrylates include,but are not limited to: cetyl-eicosyl methacrylate, which is a mixtureof hexadecyl, octadecyl, cosyl and eicosyl methacrylate; andcetyl-stearyl methacrylate, which is a mixture of hexadecyl andoctadecyl methacrylate.

The mid-cut and high-cut alkyl (meth)acrylate monomers described aboveare generally prepared by standard esterification procedures usingtechnical grades of long chain aliphatic alcohols, and thesecommercially available alcohols are mixtures of alcohols of varyingchain lengths containing between 10 and 15 or 16 and 20 carbon atoms inthe alkyl group. Examples of these alcohols are the various Zieglercatalyzed ALFOL alcohols from Vista Chemical company, i.e., ALFOL 1618and ALFOL 1620, Ziegler catalyzed various NEODOL alcohols from ShellChemical Company, i.e. NEODOL 25L, and naturally derived alcohols suchas Proctor & Gamble's TA-1618 and CO-1270. Consequently, for thepurposes of this invention, alkyl (meth)acrylate is intended to includenot only the individual alkyl (meth)acrylate product named, but also toinclude mixtures of the alkyl (meth)acrylates with a predominant amountof the particular alkyl (meth)acrylate named.

The alkyl (meth)acrylate monomers useful in the present invention may bea single monomer or a mixture having different numbers of carbon atomsin the alkyl portion. Also, the (meth)acrylamide and alkyl(meth)acrylate monomers may optionally be substituted. Suitableoptionally substituted (meth)acrylamide and alkyl (meth)acrylatemonomers include, but are not limited to: hydroxy (C₂-C₆)alkyl(meth)acrylates, dialkylamino(C₂-C₆)-alkyl (meth)acrylates,dialkylamino(C₂-C₆)alkyl (meth)acrylamides.

Substituted alkyl (meth)acrylate monomers include those with one or morehydroxyl groups in the alkyl radical, especially those where thehydroxyl group is found at the P-position (2-position) in the alkylradical. Suitable hydroxyalkyl (meth)acrylate monomers include those inwhich the substituted alkyl group is a (C₂-C₆)alkyl, branched orunbranched. Exemplary hydroxyalkyl (meth)acrylate monomers include, butare not limited to: 2-hydroxyethyl methacrylate, 2-hydroxyethylacrylate, 2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethylmethacrylate, 2-hydroxy-propyl acrylate, 1-methyl-2-hydroxyethylacrylate, 2-hydroxybutyl methacrylate, 2-hydroxybutyl acrylate andmixtures thereof.

Other substituted (meth)acrylate and (meth)acrylamide monomers includethose with a dialkylamino group or dialkylaminoalkyl group in the alkylradical. Examples of such substituted (meth)acrylates and(meth)acrylamides include, but are not limited to: dimethylaminoethylmethacrylate, dimethylaminoethyl acrylate, N,N-dimethylaminoethylmethacrylamide, N,N-dimethyl-aminopropyl methacrylamide,N,N-dimethylaminobutyl methacrylamide, N,N-di-ethylaminoethylmethacrylamide, N,N-diethylaminopropyl methacrylamide,N,N-diethylaminobutyl methacrylamide,N-(1,1-dimethyl-3-oxobutyl)acrylamide,N-(1,3-diphenyl-1-ethyl-3-oxobutyl) acrylamide,N-(1-methyl-1-phenyl-3-oxobutyl)methacrylamide, and 2-hydroxyethylacrylamide, N-methacrylamide of aminoethyl ethylene urea, N-methacryloxyethyl morpholine, N-maleimide of dimethylaminopropylamine and mixturesthereof.

Other substituted (meth)acrylate monomers useful in the presentinvention are silicon-containing monomers such as γ-propyltri(C₁-C₆)alkoxysilyl (meth)acrylate, γ-propyl tri(C₁-C₆)alkylsilyl(meth)acrylate, γ-propyl di(C₁-C₆)alkoxy(C₁-C₆)alkylsilyl(meth)acrylate, γ-propyl di(C₁-C₆)alkyl(C₁-C₆)alkoxysilyl(meth)acrylate, vinyl tri(C₁-C₆)alkoxysilyl (meth)acrylate, vinyldi(C₁-C₆)alkoxy(C₁-C₆)alkylsilyl (meth)acrylate, vinyl(C₁-C₆)alkoxydi(C₁-C₆)alkylsilyl (meth)acrylate, vinyltri(C₁-C₆)alkylsilyl (meth)acrylate, and mixtures thereof.

The vinylaromatic monomers useful as unsaturated monomers in the presentinvention include, but are not limited to: styrene, α-methylstyrene,vinyltoluene, p-methylstyrene, ethylvinylbenzene, vinylnaphthalene,vinylxylenes, and mixtures thereof. The vinylaromatic monomers alsoinclude their corresponding substituted counterparts, such ashalogenated derivatives, i.e., containing one or more halogen groups,such as fluorine, chlorine or bromine; and nitro, cyano, (C₁-C₁₀)alkoxy,halo(C₁-C₁₀)alkyl, carb(C₁-C₁₀)alkoxy, carboxy, amino,(C₁-C₁₀)alkylamino derivatives and the like.

The nitrogen-containing compounds and their thio-analogs useful asunsaturated monomers in the present invention include, but are notlimited to: vinylpyridines such as 2-vinylpyridine or 4-vinylpyridine;lower alkyl (C₁-C₈) substituted N-vinyl pyridines such as2-methyl-5-vinyl-pyridine, 2-ethyl-5-vinylpyridine,3-methyl-5-vinylpyridine, 2,3-dimethyl-5-vinyl-pyridine, and2-methyl-3-ethyl-5-vinylpyridine; methyl-substituted quinolines andisoquinolines; N-vinylcaprolactam; N-vinylbutyrolactam;N-vinylpyrrolidone; vinyl imidazole; N-vinyl carbazole;N-vinyl-succinimide; (meth)acrylonitrile; o-, m-, or p-aminostyrene;maleimide; N-vinyl-oxazolidone; N,N-dimethyl aminoethyl-vinyl-ether;ethyl-2-cyano acrylate; vinyl acetonitrile; N-vinylphthalimide;N-vinyl-pyrrolidones such as N-vinyl-thio-pyrrolidone, 3methyl-1-vinyl-pyrrolidone, 4-methyl-1-vinyl-pyrrolidone,5-methyl-1-vinyl-pyrrolidone, 3-ethyl-1-vinyl-pyrrolidone,3-butyl-1-vinyl-pyrrolidone, 3,3-dimethyl-1-vinyl-pyrrolidone,4,5-dimethyl-1-vinyl-pyrrolidone, 5,5-dimethyl-1-vinyl-pyrrolidone,3,3,5-trimethyl-1-vinyl-pyrrolidone, 4-ethyl-1-vinyl-pyrrolidone,5-methyl-5-ethyl-1-vinyl-pyrrolidone and3,4,5-trimethyl-1-vinyl-pyrrolidone; vinyl pyrroles; vinyl anilines; andvinyl piperidines.

The substituted ethylene monomers useful as unsaturated monomers is inthe present invention include, but are not limited to: vinyl acetate,vinyl formamide, vinyl chloride, vinyl fluoride, vinyl bromide,vinylidene chloride, vinylidene fluoride and vinylidene bromide.

The polymers useful as porogens in the present invention may be preparedby a variety of polymerization techniques, such as solutionpolymerization or emulsion polymerization, and preferably by solutionpolymerization. It is preferred that the polymers of the presentinvention are prepared using anionic polymerization or free radicalpolymerization techniques. The solution polymers useful in the presentinvention may be linear, branched or grafted and may be copolymers orhomopolymers. Particularly suitable solution polymers includecross-linked copolymers. Typically, the molecular weight of thesepolymers is in the range of 5,000 to 1,000,000. Exemplary molecularweight ranges are from 10,000 to 500,000, and from 10,000 to 100,000.The polydispersity of these materials is in the range of 1 to 20,preferably 1.001 to 15, and more preferably 1.001 to 10.

The solution polymers of the present invention are generally prepared ina non-aqueous solvent. Suitable solvents for such polymerizations arewell known to those skilled in the art. Examples of such solventsinclude, but are not limited to: hydrocarbons, such as alkanes,fluorinated hydrocarbons, and aromatic hydrocarbons, ethers, ketones,esters, alcohols and mixtures thereof. Particularly suitable solventsinclude dodecane, mesitylene, xylenes, diphenyl ether,gamma-butyrolactone, ethyl lactate, propyleneglycol monomethyl etheracetate, caprolactone, 2-hepatanone, methylisobutyl ketone,diisobutylketone, propyleneglycol monomethyl ether, decanol, andt-butanol.

The solution polymers of the present invention may be prepared by avariety of methods, such as those disclosed in U.S. Pat. No. 5,863,996(Graham) and European Patent Application EP 1 088 848 (Allen et al.).The emulsion polymers useful in the present invention are generallyprepared the methods described in Allen et al.

The polymer particle porogens of the present invention includecross-linked polymer chains. Any amount of cross-linker is suitable foruse in the present invention. Typically, the porogens of the presentinvention contain at least 1% by weight, based on the weight of theporogen, of cross-linker. Up to and including 100% cross-linking agent,based on the weight of the porogen, may be effectively used in theparticles of the present invention. It is preferred that the amount ofcross-linker is from 1% to 80%, and more preferably from 1% to 60%. Itwill be appreciated by those skilled in the art that as the amount ofcross-linker in the porogen increases, the conditions for removal of theporogen from the dielectric matrix may change.

Suitable cross-linkers useful in the present invention include di-,tri-, tetra-, or higher multi-functional ethylenically unsaturatedmonomers. Examples of cross-linkers useful in the present inventioninclude, but are not limited to: trivinylbenzene, divinyltoluene,divinylpyridine, divinylnaphthalene and divinylxylene; and such asethyleneglycol diacrylate, trimethylolpropane triacrylate,diethyleneglycol divinyl ether, trivinylcyclohexane, allyl methacrylate,ethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate,propyleneglycol dimethacrylate, propyleneglycol diacrylate,trimethylolpropane trimethacrylate, divinyl benzene, glycidylmethacrylate, 2,2-dimethylpropane 1,3 diacrylate, 1,3-butylene glycoldiacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanedioldiacrylate, diethylene glycol diacrylate, diethylene glycoldimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanedioldimethacrylate, tripropylene glycol diacrylate, triethylene glycoldimethacrylate, tetraethylene glycol diacrylate, polyethylene glycol 200diacrylate, tetraethylene glycol dimethacrylate, polyethylene glycoldimethacrylate, ethoxylated bisphenol A diacrylate, ethoxylatedbisphenol A dimethacrylate, polyethylene glycol 600 dimethacrylate,poly(butanediol) diacrylate, pentaerythritol triacrylate,trimethylolpropane triethoxy triacrylate, glyceryl propoxy triacrylate,pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate,dipentaerythritol monohydroxypentaacrylate, and mixtures thereof Silylcontaining monomers that are capable of undergoing cross-linking mayalso be used as cross-linkers, such as, but not limited to,divinylsilane, trivinylsilane, dimethyldivinylsilane,divinylmethylsilane, methyltrivinylsilane, diphenyldivinylsilane,divinylphenylsilane, trivinylphenylsilane, divinylmethylphenylsilane,tetravinylsilane, dimethylvinyldisiloxane, poly(methylvinylsiloxane),poly(vinylhydrosiloxane), poly(phenylvinylsiloxane), tetraallylsilane,1,3-dimethyl tetravinyldisiloxane, 1,3-divinyl tetramethyldisiloxane andmixtures thereof.

Substantially compatibilized porogens, typically have a molecular weightin the range of 5,000 to 1,000,000, such as from 10,000 to 500,000, andmore typically 10,000 to 100,000. The polydispersity of these materialsis in the range of I to 20, preferably 1.001 to 15, and more preferably1.001 to 10. Typically, the useful particle size range for thecross-linked polymeric porogen particles described above is up to 1,000nm, such as that having a mean particle size in the range of 0.5 to 1000nm. It is preferred that the mean particle size is in the range of 0.5to 200 nm, more preferably from 0.5 to 50 nm, and most preferably from 1nm to 20 nm.

Suitable block copolymers having labile components are those disclosedin U.S. Pat. Nos. 5,776,990 and 6,093,636. Such block copolymers may beprepared, for example, by using as pore forming material highly branchedaliphatic esters that have functional groups that are furtherfunctionalized with appropriate reactive groups such that thefunctionalized aliphatic esters are incorporated into, i.e.copolymerized with, the vitrifying polymer matrix.

When the removable porogens are not components of a block copolymer,they may be combined with the B-staged organic polysilica resin by anymethods known in the art. Typically, the B-staged material is firstdissolved in a suitable solvent, such as methyl isobutyl ketone,diisobutyl ketone, 2-heptanone, γ-butyrolactone, γ-caprolactone, ethyllactate propyleneglycol monomethyl ether acetate,propyleneglycol-monomethyl ether, diphenyl ether, anisole, n-amylacetate, n-butyl acetate, cyclohexanone, N-methyl-2-pyrrolidone,N,N′-dimethylpropyleneurea, mesitylene, xylenes, or mixtures thereof toform a solution. The porogens are then dispersed or dissolved within thesolution. The resulting composition (e.g. dispersion, suspension orsolution) is then deposited on a substrate by methods known in the artfor depositing B-staged dielectric materials.

The coating enhancers are typically added to the B-staged organicpolysilica resins in an amount sufficient to provide the desireduniformity and pinhole defect-free cap layers. For example, the coatingenhancers may be added to the B-staged materials in any amount of from 1to 90 wt %, based on the weight of the B-staged material, preferablyfrom >3 wt %, more preferably ≧5 wt %, and even more preferably from ≧10wt %. There is no real upper limit on the amount of coating enhancerthat can be used. It is preferred to use the lowest amount of coatingenhancer that provides the desired cap layer quality. For example,certain coating enhancers may raise the dielectric constant of the caplayer. As an overall low dielectric constant is desired for the device,it is preferred to the least amount of such coating enhancers requiredto provide the desired pinhole defect-free cap layer, to avoidunnecessarily increasing the overall dielectric constant of thedielectric layer-cap layer stack. Alternatively, it may be desired touse a coating enhancer such as a removable porogen which may provide aporous cap layer, thus reducing the dielectric constant of the cap layeras well as the overall dielectric constant of the dielectric layer-caplayer stack. When a compatibilized polymeric porogen is used as thecoating enhancer, it is preferably used in an amount of >3 wt % to 25 wt%, more preferably 5 to 20 wt % and still more preferably 8 to 15 wt %.

The cap layer compositions may further include one or more organicsolvents. A solvent is preferred. Any solvent that dissolves, disperses,suspends or otherwise is capable of delivering the B-staged organicpolysilica resin and the coating enhancer to the substrate is suitable.Such organic solvents are well known in the art and include, but are notlimited to, ketones such as methyl isobutyl ketone, diisobutyl ketone,cyclohexanone, and 2-heptanone, lactones such as γ-butyrolactone andγ-caprolactone, esters such as ethyl lactate, propyleneglycol monomethylether acetate, n-amyl acetate, n-butyl acetate, ethers such as diphenylether and anisole, glycol ethers such as propyleneglycol monomethylether, N-methyl-2-pyrrolidone, N,N′-dimethylpropyleneurea, aromatichydrocarbons such as mesitylene, toluene, and xylenes, and mixtures ofsolvents. Alternatively, solvents may consist of highly pressurizedgases, such as supercritical carbon dioxide, with one or moreco-solvents or additives to provide the desired solvency properties. Itis preferred that a composition including one or more B-staged organicpolysilica materials and one or more organic solvents is disposed on asubstrate. Once such a composition is disposed on the substrate, thesolvent may be removed prior to or during the step of curing theB-staged organic polysilica material.

The cap layer compositions may further include one or more additionalcomponents, such as inorganic compounds. Suitable inorganic compoundsinclude, but are not limited to silica, alumina, ceria, zirconia,silicon carbide, silicon nitride and the like, including mixturesthereof. Such inorganic particles may be very fine (ultrafine) powders,sols, colloids, or in any other suitable form. As an example, silica,alumina, and zirconia may be synthesized by a fumed method in whichoxygen and hydrogen are reacted with silicon chloride, aluminum chlorideor titanium chloride in a gas phase. A sol-gel method may be also beused. In this method, a metal alkoxide such as tetraethoxysilane or analuminum alkoxide is hydrolyzed and condensation is performed. Colloidalsilica is a dispersion of highly pure silicic anhydride in a hydrophilicorganic solvent, such as with a solids content in the range of 10 to40%, where the silica particles have an average diameter of 5 to 30 nmand preferably 10 to 20 nm. Colloidal silica, such as methanol silicasol or iso-propanol silica sol, and colloidal alumina are generallycommercially available, such as from Nissan Chemical Industries, Ltd.

Alternatively, the inorganic compounds may be co-condensed orco-hydrolyzed with any of the above described silicon-containingmonomers, oligomers or polymers. Metal alkoxides are typically used asthe inorganic compounds for use in such co-condensations orco-hydrolyses. Cerium alkoxides, aluminum alkoxides and zirconiumalkoxides are the most useful metal alkoxides for this application.Useful alkoxide moieties are (C₁-C₆)alkoxides and more particularly(C₁-C₃)alkoxides.

One or more stabilizing compounds for the B-staged organic polysilicaresin may also be used in the cap layer compositions. Such stabilizingcompounds typically stabilize the organic polysilica resin againstpremature condensation or polymerization. Suitable stabilizing compoundsinclude, but are not limited to, organic acids having 2 carbons or moreand having a pKa of 1 to 4, and organic acids capable of functioning asa chelating agent. The amount of such stabilizing compounds is in therange of I to 10,000 ppm and preferably 5 to 5000 ppm.

Other optional components that may be added to the present cap layercompositions include, but are not limited to, copper chelating agents,base curing agents, acid curing agents and the like. Any useful copperchelating agent may be used, such as hydroxylamine, hydroxylaminederivatives, benzotriazole, and the like. Base curing agents include,bases, thermal base generators and photobase generators. Complexes ofbases with certain acids may also be suitable base curing agents. Suchbase curing agents are well known to those skilled in the art. Acidcuring agents include thermal acid generators and photoacid generators.The useful acid curing agents are well-known to those skilled in theart. The amount of such optional base and acid curing agents present inthe compositions is typically small, such as in catalytic quantities andare well within the abilities of those in the art.

The cap layer compositions are disposed on a dielectric substrate by anysuitable means, such as, but not limited to, spin coating, spray coatingor doctor blading. Spin coating is preferred. Such disposing meanstypically provide a film, layer or coating of B-staged material. Thedielectric substrate may be partially cured or fully cured. The onlyconcern being that the dielectric substrate is sufficiently cured toprevent intermixing with the cap layer composition.

Any dielectric material used in the manufacture of electronic devices,such as integrated circuits, may benefit from the cap layer of thepresent invention. Suitable dielectric materials include, but are notlimited to organic polysilica materials, silicon dioxide, fluorinatedsilicon dioxide, benzocyclobutenes, poly(arylene ethers), poly(arylesters), poly(ether ketones), polycarbonates, polyimides, fluorinatedpolyimides, polynorbornenes, polyaromatic hydrocarbons such aspolynaphthalene, polyquinoxalines, poly(perfluorinated hydrocarbons)such as poly(tetrafluoroethylene), and polybenzoxazoles. Suitableorganic polysilica dielectric materials are any having the compositionsdescribed above. Preferably, the dielectrics are porous. Porous organicpolysilica dielectrics are well known and are disclosed in U.S. Pat. No.6,271,273 (You et al.) and U.S. Pat. No. 5,895,263 (Carter et al.). Inone embodiment, the dielectric material is a thermally degradablematerial, which can be subsequently selectively removed during furtherprocessing of an electronic device, i.e. after curing of any applied caplayer. Suitable thermally degradable polymers are those disclosed inU.S. Pat. No. 6,165,890 (Kohl et al.).

Once the cap layer composition is applied to the dielectric substrate,the solvent is removed such as by heating at a temperature of 90° to150° C. for 10 to 120 seconds. The cap layer is then typically softbaked at a temperature of 150° to 250° for 10 to 360 seconds to at leastpartially cure the cap layer.

Sufficient cap layer composition is typically applied to the dielectricsubstrate to provide a cap layer having a desired thickness. Typicalthicknesses range from 100 to 1000 Å and preferably from 400 to 600 Å.

More than one cap layer may be used according to the present invention.For example, a second cap layer may be applied to the present cap layerto provide a dual cap layer structure. The second cap layer may be anyconventional cap layer such as organic polysilica cap layer, silicondioxide, silicon carbide, silicon oxynitride, silicon nitride, siliconoxycarbide, polyarylene ethers, and the like. Alternatively, the presentorganic polysilica cap layers may be used as the second cap layer of adual cap layer structure (or the second or third cap layer of a threecap layer structure, etc.) In such application, the present organicpolysilica cap layer composition is disposed on a cap layer which isdisposed on a dielectric layer. In one embodiment, where two organicpolysilica cap layers are used, it is preferred that the first (or caplayer adjacent the dielectric layer) cap layer have a higher siliconcarbide content that the second (or upper) cap layer.

To be useful as coating enhancers in the present invention, suchcompounds, if they remain in the cap layer following final cure, mustnot interfere with or adversely affect the properties of the cap layer.Preferably, such coating enhancers are at least partially removableunder conditions which do not adversely affect the organic polysilicamaterial, preferably substantially removable, and more preferablycompletely removable. The coating enhancers may be removed prior, duringor after complete or final curing of the cap layer material. Preferably,the coating enhancers are removed prior to or during the step ofcompletely curing (final cure) the organic polysilica cap layermaterial, and more preferably during the final curing step. When the caplayer needs to be dense to fulfill its function, the coating enhancersare typically removed after such function has been fulfilled. By“removable” is meant that the coating enhancer volatilizes,depolymerizes or otherwise breaks down into volatile components orfragments which are then removed from, or migrate out of, the organicpolysilica material. Any procedures or conditions which at leastpartially remove the coating enhancer without substantially degradingthe organic polysilica material, that is, where less than 5% by weightof the dielectric material is lost, may be used. It is preferred thatthe coating enhancer is substantially removed. Suitable methods ofremoving the coating enhancers are those used for the removal ofporogens. Typical methods of removal include, but are not limited to:exposure to heat, vacuum, pressure or radiation such as, but not limitedto, actinic, IR, microwave, UV, x-ray, gamma ray, alpha particles,neutron beam or electron beam. It will be appreciated that more than onemethod of removing the coating enhancer may be used, such as acombination of heat and actinic radiation. It is preferred that theorganic polysilica material is exposed to heat or UV light to remove thecoating enhancer. It will also be appreciated by those skilled in theart that other methods of coating enhancer removal, such as by atomabstraction, may be employed.

The coating enhancers can be thermally removed under vacuum, nitrogen,argon, mixtures of nitrogen and hydrogen, such as forming gas, or otherinert or reducing atmosphere, air as well as under oxidizingatmospheres. The coating enhancers may be removed at any temperaturethat is higher than the thermal curing temperature and lower than thethermal decomposition temperature of the organic polysilica material.Typically, the polymeric porogen coating enhancers may be removed attemperatures in the range of 150° to 450° C. and preferably in the rangeof 250° to 425° C. Under preferable thermal removal conditions, theorganic polysilica material is heated to a temperature of 350° to 400°C. It will be recognized by those skilled in the art that the particularremoval temperature of a coating enhancer will vary according tocomposition of the coating enhancer. Such heating may be provided bymeans of an oven or microwave. Typically, the coating enhancers of thepresent invention are removed upon heating for a period of time in therange of 1 to 120 minutes. After removal from the organic polysilicamaterial, 0 to 20% by weight of the coating enhancer typically remainsin the porous organic polysilica material. In another embodiment, when acoating enhancer is removed by exposure to radiation, the coatingenhancer is typically exposed under an inert atmosphere, such asnitrogen, to a radiation source, such as, but not limited to, visible orultraviolet light.

In one embodiment, the coating enhancers are removed from the partiallycured cap layer. In this process, the cap layer is heated in a furnaceto the desired curing temperature, e.g. 350° to 500° C. and preferablyfrom 400° to 475° C., for a period of time sufficient to complete theorganic polysilica curing process. Such times are well known to thoseskilled in the art. During such final cure step, the coating enhancersmay also be removed. In general, when such volatile materials are movedfrom a fully cured dielectric material, pores or voids remain.Accordingly, porous organic polysilica cap layers are obtained.

The pores in such porous organic polysilica cap layers are substantiallythe same size as that of the coating enhancer used, particularly whenthe coating enhancer is a porogen particle. The pore size of the poresin the porous organic polysilica material made by a removable coatingenhancer is from 0.5 to 1000 nm, preferably from 0.5 to 200 nm, morepreferably from 1 to 50 nm, and still more preferably from 1 to 20 nm.

The present invention provides a structure comprising a first layer of adielectric material and a cap layer disposed on the dielectric layer,wherein the cap layer is porous. Such cap layer typically has a porositysubstantially equal to the amount of porogen used. The cap layer ispreferably an organic polysilica cap layer. It is also preferred thatthe dielectric layer is porous. It is further preferred that thedielectric layer in such structure is an organic polysilica dielectricmaterial. Also provided by this invention is a structure comprising aporous first layer of an organic polysilica dielectric material and aporous cap layer disposed on the dielectric material. Preferably, suchcap layer comprises an organic polysilica material.

In general, the porous cap layers of the present invention have areduced dielectric constant as compared to the same cap layer that isnon-porous. Useful organic polysilica cap layers are those having adielectric constant of ≦3, preferably ≦2.9, more preferably ≦2.8 andstill more preferably in the range of 2.5 to 2.8.

The cap layers of the present invention are particularly useful with lowdielectric constant (k≦3) dielectric materials. Structures comprising adielectric layer having a dielectric constant of ≦3 and an organicpolysilica cap layer disposed on the dielectric layer, wherein theorganic polysilica cap layer has a dielectric constant of ≦2.9. Suchdielectric layers preferably include dielectric materials having adielectric constant of ≦2.8 and more preferably ≦2.5.

In general, a cap layer has an etch selectivity of 3:1 to 10:1 orgreater as compared to the dielectric material it is disposed on.Preferably, the etch selectivity is 5:1 or greater. The particular caplayer B-staged organic polysilica resin is selected to provide such anetch differential with the dielectric layer to which it is applied. Whenan organic polysilica cap layer is used with an organic polysilicadielectric material such as methyl silsesquioxane, the cap layer organicpolysilica is selected so as to have a higher silicon content to providethe requisite etch differential.

The cap layers of the present invention are typically selected such thatthe difference in etch selectivities between the cap layer and thedielectric layer on which it is disposed is 10% or greater, preferably20% or greater and more preferably 40% or greater. This is particularlythe case when the dielectric layer is a porous organic polysilicamaterial. In a further embodiment, the present invention provides astructure comprising a porous first layer of an organic polysilicadielectric material having a first etch selectivity and a porous caplayer disposed on the dielectric material having a second etchselectivity, wherein the difference in etch selectivities is 10% orgreater. Also provided are structures comprising a dielectric layerhaving a density of ≦1 g/L and a cap layer disposed on the dielectriclayer and having a density of ≧1 g/L. Preferably such cap layers areorganic polysilica materials. Such organic polysilica cap layerspreferably have a density of ≧1.1, and more preferably ≧1.2 g/L.

In a typical process, a dielectric composition, such as a B-stagedorganic polysilica resin including a porogen (a plurality of polymericporogen particles), is disposed on a substrate. The B-staged dielectricresin is then at least partially cured at a temperature of up to 250° C.to form the dielectric substrate. A present cap later composition isthen disposed, such as by spin coating, on the partially cured organicpolysilica dielectric material to provide a two-layer stack orstructure. The stack is then set by either partially curing the caplayer or fully curing the materials in the stack at high temperature(≧400° C.). The polymeric porogen is removed from the organic polysilicadielectric material during the final curing step. Likewise, the caplayer coating enhancer is removed during the final curing step.Preferably, the porogen used in the B-staged organic polysilicadielectric material is the same as the coating enhancer used in the caplayer composition. Such process has the advantage of a reduced number ofsteps as compared to fully curing each layer individually, as well asproviding improved adhesion between the organic polysilica dielectricmaterial and the cap layer material.

Alternatively, the dielectric material may be fully cured prior todisposing the present cap layer compositions on the dielectricsubstrate.

The present cap layers are useful in the manufacture of electronicdevices, particularly integrated circuits. In such manufacturingprocess, a low dielectric constant dielectric material is disposed on asubstrate; the low dielectric constant dielectric material is then atleast partially cured to form a dielectric material layer; a cap layercomposition including a B-staged organic polysilica resin and a coatingenhancer is disposed on the dielectric material layer, wherein thecoating enhancer is present in an amount sufficient to provide apinhole-free cap layer; the B-staged organic polysilica resin is atleast partially curing the to form a cap layer; the coating enhancer isoptionally removed; and the cap layer is the optionally completelycured. Such cap layer may then have another cap layer disposed on it, asdescribed above. Alternatively, a pattern may be formed in the caplayer. Such patterning typically involves (i) coating the cap layer witha positive or negative photoresist, such as those marketed by ShipleyCompany; (ii) imagewise exposing, through a mask, the photoresist toradiation, such as light of appropriate wavelength or e-beam; (iii)developing the image in the resist, e.g., with a suitable developer; and(iv) transferring the image through the cap layer to the substrate witha suitable transfer technique such as reactive ion etching. Such etchingcreates apertures in the cap layer and the dielectric material.Optionally, an antireflective coating is disposed between thephotoresist layer and the cap layer. In the alternative, anantireflective coating may be applied to the surface of the photoresist.Such lithographic patterning techniques are well known to those skilledin the art.

While the above description has been written exemplifying an organicpolysilica material as the cap layer material, it will be appreciated bythose skilled in the art that the present coating enhancers may be usedfor other spin-on or liquid applied cap layer materials, such ashydrogen silsesquioxane, spin-on glasses, i.e. silicon dioxideprecursors, poly(arylene ethers) and the like.

The following examples are presented to illustrate further variousaspects of the present invention, but are not intended to limit thescope of the invention in any aspect.

EXAMPLE 1

Silicon wafers (8 inch or 20 cm diameter) were spin coated with anorganic polysilica composition containing 30% solids of methylsilsesquioxane co-condensed with a tetraalkoxyorthosilicate in anorganic solvent using a commercially available coating track. Theorganic polysilica composition contained 22.5% of a compatible porogenby weight. The composition was spin coated on the wafers at 200 rpm andthen a film was spread to a thickness of ca. 4000 Å at 3000 rpm. Excessmaterial was removed from the back side of the wafer using aconventional edge bead remover and back side rinse agent. The films werethen processed on a hot plate at 90° C. to partially remove the solvent,followed by heating at 230° C. to partially cure the organic polysilicalayer.

EXAMPLE 2 (COMPARATIVE)

An organic polysilica cap layer composition containing 3% w/w of acopolymer of methyl silsesquioxane-tetraethylorthosilicate (55:45 molarratio, with a molecular weight of ca. 6500) in propyleneglycolmonomethyl ether acetate with 150 ppm of an acid stabilizer wasprepared. The cap layer film has an atom-weight composition of 43% w/wsilicon and 10% w/w carbon, which provided an etch selectivity of 5x tolOx as compared to the organic polysilica dielectric layer.

The cap layer composition was deposited on a wafer sample from Example 1by spin coating (2500 rpm) and had a thickness of ca. 440-550 Å. Thesample was then cured in a furnace at 450° C. The surface of theresulting cap layer was analyzed by scanning electron microscopy for thepresence of pinhole defects using a KLA-Tencor instrument at 200,000magnification. FIG. 1 is a SEM of this cap layer which clearly shows thepresence of pinhole defects.

EXAMPLE 3

The procedure of Example 2 was repeated except that the cap layercomposition further included 3% by weight of a compatibilized polymericporogen as a coating enhancer. The porogen was a copolymer ofPPG260MA/trimethylene glycol dimethacrylate (90/10). “PPG260MA” refersto a polypropyleneglycol ester of methacrylic acid, where thepolypropyleneglycol has an average molecular weight of 260. Followingfurnace curing, the surface of the cap layer was evaluated. FIG. 2 is aSEM of this cap layer which still shows the presence of pinhole defects.The amount of the coating enhancer is insufficient to provide a pinholedefect-free film.

EXAMPLE 4

The procedure of Example 2 was repeated except that 10% by weight of thecompatibilized polymeric porogen was used as the coating enhancer. FIG.3 is a SEM of this cap layer which still shows the surface to be free ofpinhole defects.

1-10. (canceled)
 11. A structure comprising a first layer of an organicpolysilica dielectric material and a second layer disposed on the firstlayer, wherein the second layer is a composition comprising one or moreB-staged organic polysilica resins and one or more removable porogens,wherein the removable porogens are present in an amount sufficient toprovide a pinhole-free second layer.
 12. A structure comprising a layerof a dielectric material and porous cap layer disposed on the dielectricmaterial.
 13. The structure of claim 12 wherein the cap layer comprisesan organic polysilica material.
 14. The structure of claim 12 whereinthe dielectric material is porous.
 15. The structure of claim 14 whereinthe dielectric material comprises an organic polysilica material. 16.The structure of claim 12 wherein the dielectric material has a firstetch selectivity and the porous cap layer disposed on the dielectricmaterial has a second etch selectivity, wherein the etch selectivitieshave a difference of 10% or greater.
 17. A structure comprising adielectric layer having a dielectric constant of ≦3 and an organicpolysilica cap layer disposed on the dielectric layer, wherein theorganic polysilica cap layer has a dielectric constant of ≦2.9.
 18. Thestructure if claim 17 wherein the dielectric layer is porous.
 19. Thestructure of claim 17 wherein the organic polysilica cap layer isporous.